Method and device for protecting a camera from soiling and printing installation therewith

ABSTRACT

The invention relates to a method of protecting a camera ( 2 ) for inspecting printed work during printing from soiling. A transparent protective element ( 7 ) is placed here between the camera ( 2 ) and the printed work for inspection, and the protective element ( 7 ) is replaced when the transparency thereof decreases. The transparent protective element ( 7 ) can form part of a strip of transparent film ( 7 ) which is unwound from a supply reel ( 9 ) and wound onto a take-up reel ( 10 ). The decrease in transparency can be determined on the basis of a recording made by the camera ( 2 ). The invention also relates to a device ( 1 ) for protecting such a encamera ( 2 ) from soiling, comprising a transparent protective element ( 7 ) to be placed between the camera ( 2 ) and the printed work for inspection; and means () for replacing the protective element ( 7 ) when the transparency thereof decreases. The replacing means ( 8 ) can comprise a strip of transparent material ( 7 ) supplied on a supply reel ( 9 ) and be configured to unwind the film ( 7 ) from a supply reel ( 9 ) and wind it onto a take-up reel ( 10 ). The supply reel ( 9 ) and the take-up reel ( 10 ) can be received in a cassette ( 3 ) which has between the supply reel ( 9 ) and the take-up reel ( 10 ) an opening ( 4 ) along which the transparent film ( 7 ) is moved. Finally the invention further relates to a printing installation in which a camera ( 2 ) with such a protective device ( 1 ) is applied.

The invention relates to a method for protecting a camera from soilingand to a device for performing this method.

In the graphic industry, particularly during production of printed workon rotary offset printing presses, cameras are used to measure quality.There are different cameras for different functions, such as colourregister, cutting register, colour measurement and the like.

Because these cameras become soiled quite quickly by the printingproduction process, various solutions have been proposed to minimize thesoiling and to enable quick cleaning of soiled cameras.

Methods thus exist for minimizing soiling by blowing air in front of thecamera. There are also removable glass slides to enable quick and propercleaning of the soiled cameras.

Some cameras even travel in a “dog house”, where they are cleaned. Thiscan for instance be done by means of a brush or by means of an airpulse.

Because there is no definitive solution to soiling and the cameraseventually become soiled anyway, maintenance will always be required.Maintenance costs are a problem, particularly for the processes wheremany cameras are used and few people remain involved in the productionprocess.

The invention now has for its object to provide a method with which acamera can be protected from soiling. This is achieved according to theinvention by placing a transparent protective element in front of thecamera, in particular between the camera and the printed work forinspection, and replacing the protective element when the transparencythereof decreases.

Interposing of this protective element prevents soiling in effectivemanner, while regular replacement prevents the recording quality of thecamera being adversely affected by the presence of the protectiveelement.

The transparent protective element preferably forms part of a supply oftransparent material and is replaced by placing another part of thesupply of transparent material in front of the camera. The transparentmaterial can thus be replaced without having to interrupt the operationof the camera.

The transparent material can here advantageously be moved along stepwisein front of the camera.

When the supply of transparent material comprises a strip of transparentfilm which is unwound from a supply reel and wound onto a take-up reel,replacement of the protective element can be performed in very simplemanner. In order to enable undisturbed use being made of the camera, thesupply reel can be exchanged here when the strip of transparent film hasbeen substantially fully unwound.

This exchange can be realized quickly and easily when the supply reeland the take-up reel are received in a cassette and the supply reel isexchanged by changing the cassette.

Although the transparency of the protective element could be measuredand monitored separately, it is simpler for the decrease in transparencyto be determined on the basis of a recording made with the camera. Asimple and reliable monitoring is achieved when the decrease in thetransparency is determined on the basis of definition and/or colour ofthe recording.

The invention also relates to a device for protecting a camera fromsoiling, particularly a camera for inspecting printed work duringprinting. According to the invention such a device comprises atransparent protective element to be placed in front of the camera, inparticular between the camera and the printed work for inspection, andmeans for replacing the protective element when the transparency thereofdecreases.

Preferred embodiments of this protective device according to theinvention form the subject-matter of the dependent claims 1-20.

Finally, the invention further relates to a printing installation inwhich a camera with such a protective device is applied.

The invention is now elucidated on the basis of two embodiments, whereinreference is made to the accompanying drawing, in which:

FIG. 1 is a schematic top view of a camera with a device according tothe invention,

FIG. 2 is a schematic front view of the protective device of FIG. 1,

FIG. 3 is a perspective view of a variant of the protective device, and

FIG. 4 shows a cross-section through the protective device of FIG. 4.

A device 1 for protecting against soiling of a camera 2, particularly acamera for inspecting printed work during printing, comprises anexchangeable cassette 3 for placing between camera 2 and the printedwork for inspection. Formed in cassette 3, which can be releasablyconnected to camera 2, is an opening 4 which lies in register withoptical component 5 and lighting means 6 of camera 2. This opening 4 isclosed off by a transparent protective element 7 which can be replacedwhen the transparency thereof decreases.

Protective device 1 is provided for this purpose with means 8 forreplacing protective element 7. In the shown embodiment the replacingmeans 8 comprise a supply of transparent material, of which thetransparent protective element 7 forms part. Replacing means 8 areconfigured to move the transparent material along stepwise in front ofcamera 2. The supply of transparent material is here a film wound onto asupply reel 9 and guided along opening 4 to a take-up reel 10. Replacingmeans 8 comprise a winding motor 11 connected to take-up reel 10 andcontrolled by means for detecting the transparency of the part of thefilm which is present in front of opening 4 and there forms thetransparent protective element 7.

These detection means are incorporated in or co-act with camera 2, sincein the shown embodiment the decrease in the transparency is determinedon the basis of definition and/or colour of recordings made by camera 2.Each time it is determined that a recording has insufficient definitionor is for instance too dark, camera 2 sends a signal to winding motor11. This signal indicates that film 7 in front of the lens is soiled andis used to refresh the film in front of camera 2. The soiled film iswound onto take-up reel 10 in cassette 3.

Before supply reel 9 with clean film in cassette 3 is fully used up, awarning signal is sent that cassette 3 has to be exchanged. Cassette 3is then removed and replaced by a new cassette. With normal use thisneed take place only several times a year.

In the embodiment of FIGS. 3 and 4 the single relatively large opening 4in cassette 3 is replaced by a smaller central opening 4A, the shape ofwhich is adapted to a double lens in camera 2, and two smaller elongateopenings 4B for the lighting. Film 7 is thus also guided and supportedin the centre by wall parts 12 of cassette 3 present between openings4A, 4B. Deformation of the film 7, which could affect the quality of therecording, is hereby prevented.

Although the invention has been elucidated above on the basis of twoembodiments, it will be apparent that it is not limited thereto. Othertypes of transparent protective element can also be envisaged, forinstance plastic sheets or even thin glass plates. Other movements ofthe protective elements along the camera can also be envisaged, forinstance a rotating movement in a plane in front of the camera.

The invention is therefore defined solely by the following claims.

1. Method for protecting a camera from soiling, in particular a camerafor inspecting printed work during printing, by placing a transparentprotective element in front of the camera, in particular between thecamera and the printed work for inspection, and replacing the protectiveelement when the transparency thereof decreases.
 2. Method as claimed inclaim 1, characterized in that the transparent protective element formspart of a supply of transparent material and is replaced by placinganother part of the supply of transparent material in front of thecamera.
 3. Method as claimed in claim 2, characterized in that thetransparent material is moved along stepwise in front of the camera. 4.Method as claimed in claim 2 or 3, characterized in that the supply oftransparent material comprises a strip of transparent film which isunwound from a supply reel and wound onto a take-up reel.
 5. Method asclaimed in claim 4, characterized in that the supply reel is exchangedhere when the strip of transparent film has been substantially fullyunwound.
 6. Method as claimed in claim 5, characterized in that thesupply reel and the take-up reel are received in a cassette and thesupply reel is exchanged by changing the cassette.
 7. Method as claimedin any of the foregoing claims, characterized in that the decrease intransparency is determined on the basis of a recording made with thecamera.
 8. Method as claimed in claim 7, characterized in that thedecrease in the transparency is determined on the basis of definitionand/or colour of the recording.
 9. Device for protecting a camera fromsoiling, particularly a camera for inspecting printed work duringprinting, comprising a transparent protective element to be placed infront of the camera, in particular between the camera and the printedwork for inspection, and means for replacing the protective element whenthe transparency thereof decreases.
 10. Device as claimed in claim 9,characterized in that the replacing means comprise a supply oftransparent material of which the transparent protective element formspart, and the replacing means are configured to place another part ofthe supply of transparent material in front of the camera when thetransparency of the transparent protective element decreases.
 11. Deviceas claimed in claim 10, characterized in that the replacing means areconfigured to move the transparent material along stepwise in front ofthe camera.
 12. Device as claimed in claim 10 or 11, characterized inthat the supply of transparent material comprises a strip of transparentfilm supplied on a supply reel and the replacing means are configured tounwind the film from the supply reel and wind it onto a take-up reel.13. Device as claimed in claim 12, characterized in that the replacingmeans comprise a winding motor connected to the take-up reel.
 14. Deviceas claimed in claim 12 or 13, characterized in that the supply reel andthe take-up reel are received in a cassette which has between the supplyreel and the take-up reel at least one opening along which thetransparent film is moved.
 15. Device as claimed in claim 14,characterized in that the at least one opening lies in register with anoptical component and/or lighting means of the camera.
 16. Device asclaimed in claim 15, characterized by at least two openings, at leastone of which lies in register with the optical component and at leastone with the lighting means.
 17. Device as claimed in any of the claims14-16, characterized in that the cassette is connected releasably to thecamera.
 18. Device as claimed in any of the claims 9-17, characterizedby means connected in controlling manner to the replacing means fordetecting the transparency of the transparent protective element. 19.Device as claimed in claim 18, characterized in that the detecting meansare configured to determine the transparency on the basis of a recordingmade with the camera.
 20. Device as claimed in claim 19, characterizedin that the detecting means are configured to determine the transparencyon the basis of definition and/or colour of the recording.
 21. Printinginstallation, comprising at least one printing press, a control deviceconnected thereto and at least one camera connected to the controldevice for monitoring printed work produced by the installation, thecamera being provided with a device as claimed in any of the claims9-20.